Clarent is an immensely powerful Sword of Power that is linked to elemental fire magic. The weapon, carved out of stone, is rough, dull-grey, and about three feet in length. Despite the material generally being vulnerable to weathering and shattering, the weapon is effectively impossible to destroy. Along with the other three swords, Clarent is/was reforged into Marethyu'sHook of Aether.

Clarent got its nickname, the Coward's Blade, because it was used by Mordred to kill King Arthur.

Powers

Corruption: Prolonged use of the swords can damage the mind of the wielder. Mars Ultor, Mordred, and Cernunnos were corrupted and nearly destroyed by the swords.

Telepathic Linking: Wounding or killing something with one of the swords of power will allow partial access to the memories and experiences of whatever the sword was connected with.

Killing: Like the other swords of power, Clarent can kill almost anything. Some things (such as Coatlicue) may be immune to its power, however the sword was capable of killing the Nidhogg.

Creation of Ley Lines: Together the swords of power are capable of creating ley lines and ley gates. For instance, Dr. John Dee created a portal into Coatlicue's Shadowrealm using the four swords together.

The Magician

In The Magician, Nicholas Flamel gives Josh Clarent because he has not yet been awakened. Scathach and Joan of Arc begin to teach Josh how to use it, which he finds harder than he thought. Soon after, Josh uses Clarent to fight the Nidhogg and also saves Scathachs life. However he drops Clarent, which is soon retrieved by Nicholas Flamel.

Josh Newman carries the sword in a battle against Dr. John Dee. Dee holds Excalibur. The two fight difficultly with the twin blades. Josh at one point grabs hold of both twin swords and is blown away with power. Clarent is stuck to his hand and he has to drop Excalibur in order to move. At this point, Dee picks up Clarent for himself.

The Necromancer

In The Necromancer, Dee carries Clarent and Excalibur while they are fused together as one. Dee almost uses it against several Cucubuths but is spared the trouble by Virginia Dare . Later Dee uses the sword(s) to create two Leygates that lead them to Pioneer Park in San Francisco, five minutes from his home. Dee later reveals to Dare that he has all four swords in his possession and intends to use them to create a leygate to Coatlicue's Shadowrealm. When Dee and Josh (in a trance) create a leygate to Coatlicue's shadowrealm, Niten, Aoife, and Sophie Newman arrive. Josh tries to use Clarent to protect Coatlicue (who appears beautiful to him) but fails. After Aoife drags Coatlicue back into her shadowrealm, Josh, Dee, and Dare escape with the four swords.

The Warlock

In The Warlock, Josh carries Clarent but does not use it. However when he is on Alcatraz Clarent tempts him to loose the monsters on the city. When Mars, Odin, Hel, and Sophie arrive on the island Dee uses the swords to create a leygate that brings them back ten thousand years to Danu Talis. There they run into Isis and Osiris who, after taking away Dee's immortality, collect the four swords.

The Enchantress

In The Enchantress, Clarent and the other three swords are collected by Isis and Osiris. Afterwards, they return them to the twins. Josh receives Clarent and Excalibur while Sophie receives Durendal and Joyeuse. Later on, Josh uses Clarent and Excalibur to kill Isis and Osiris after discovering they were not their parents and intended to use them to rule Danu Talis. Finally, Josh combines all four swords into Aether, Sword of Time, so that he can destroy Danu Talis. In doing so he becomes Death, or Marethyu.